The present invention relates to a pneumatically operated nail gun, and more particularly, to such a nail gun having an arrangement for preventing a cylinder from floating.
In a conventional nail gun, as shown in FIGS. 1 and 2, a main housing 2 and an exhaust cover 13 define an outer case. The main housing 2 is connected to the exhaust cover 13 through a separator 25. The outer case defines therein a compressed air chamber 3. A tail cover 18 is disposed at a lower end of the main housing 2. A cylinder 8 is fixed to the main housing 2, and a piston 4 having a driver blade 4A is slidably disposed in the cylinder 8 through a seal ring 5 assembled in a ring groove 4a of the piston 4. The driver blade 4A can extends through the tail cover 18 for driving a nail fed to the tail cover 18.
The lower portion of the cylinder 8 has a conical section 8a in which inner and outer diameters are gradually increased toward a tail cover 18. Further, a piston bumper 12 is disposed at the lower end of the cylinder 8 for absorbing a surplus energy of the piston 4 after the driver blade 4A strikes against the nail. The piston bumper 12 has a conical portion approximately the same as the inner configuration of the conical section 8a so as to prevent the bumper 12 from moving toward the exhaust cover 13. Compressed air is introduced into an upper space of the cylinder 8 to move a piston 4 toward a nail.
At an upper outer peripheral surface of the cylinder 8, a plurality of ribs 226 integrally protrude radially outwardly with a space in a circumferential direction of the cylinder 8. These ribs 226 are engaged with the separator 25. Thus, the cylinder 8 is fixedly supported to the main housing 2 through the separator 25 and the exhaust cover 13 so as to prevent the cylinder 8 from accidentally moving toward the exhaust cover 13.
In case of a nail driving operation, the piston bumper 12 is subjected to a small amount of force, because the nail driving power is almost consumed as a result of actual nail driving into a workpiece. On the other hand, if nail driving operation is performed without feeding a nail in the tail cover 18, all force necessary for nail driving is applied to the piston bumper 12. Thus, the piston bumper 12 is greatly deformed.
As a result of deformation, a force F exerted on the conical section 8a becomes large, so that a component of force F1 exerted on the cylinder 8 and directing toward the exhaust cover 13 is also becomes large. Thus, this component of force F1 urges the cylinder 8 upwardly. In order to resist the component of force F1, high mechanical strength or rigidity of the separator 25, the exhaust cover 13, and the main housing 2 must be required, which in turn increases in production cost and a total weight of the nail gun, and decreases in internal volume of the compressed air chamber 3.
It is an object of the present invention to overcome the above-described problems and to provide an improved nail gun capable of reducing production cost and a total weight, and ensuring an internal volume of a compressed air chamber without any increase in rigidity of the separator, the exhaust cover and the main housing.
This and other objects of the present invention will be attained by a pneumatically operated nail gun including a main housing, a cylinder, a piston, a driver blade, a plurality of ribs, a force receiving section, and a damper member. The main housing defines therein a compressed air chamber, and the cylinder is disposed in the main housing. The piston is slidably movable in the cylinder between its upper dead center and a lower dead center and divides the cylinder space into an upper cylinder space and a lower cylinder space. The driver blade extends from the piston in the lower cylinder space and is protrudable from a lower end of the main housing for striking against a head of the nail in accordance with the movement of the piston toward its lower dead center by compressed air fed from the compressed air chamber to the upper cylinder space. The plurality of ribs protrude from the cylinder radially outwardly and are spaced away from each other in a circumferential direction of the cylinder. Each rib has a seat portion. The force receiving section is positioned in confrontation with and downstream of the seat portion in a moving stroke of the piston toward its upper dead center. The damper member is interposed between the seat portion and the force receiving section.